C#•2y ago

❔ Use Variable as Type

Hiya 🙂 I'm needing some help with a WinForms Project. I want to take an object from a list and convert that object's properties to an array. The object type, however, can vary. I have a form that asks for what type the user wants, and I want to pass that decision into my code as a variable so that the correct object type is loaded. I've been using dynamic, but it mistakes one class for another, and dynamic is ugly anyway. Attached the code for that bit with dynamic in. Thanks!

26 Replies

the doctor monsterOP•2y ago

objList is the list of generic objects. objArray is an array of those objects. singleArr is just one of those objects and objProp is that object's properties.

Angius•2y ago

Well, the problem is, C# isn't really built to support "an array of whatever" object, dynamic, etc are just workarounds at best Signs of bad design, usually

the doctor monsterOP•2y ago

oh bugger

Angius•2y ago

So if your list can hold whatever in it, I have to question why

the doctor monsterOP•2y ago

I have 2 classes customer and engineer there is a data entry form and it will add it to a list and csv

Angius•2y ago

Seems like they could both inherit from a Person class

the doctor monsterOP•2y ago

indeed they do

Angius•2y ago

Or even they could just be a Person class With a property that tells you whether they're a customer or an engineer

the doctor monsterOP•2y ago

there as about 3 properties different ooh and then I could just leave the customer specific properties balnk? blank?**

Angius•2y ago

Sure Or you can have a list of Person And use pattern matching to see if they're the customer or engineer

the doctor monsterOP•2y ago

could I just google microsoft documentation about pattern matching? I haven't used that before but sounds usefull i ask that and it took 2 secs to actually do it

Angius•2y ago

Sure can google it lol Basically, what it lets you do, is

if (person is Client c)
{
    Console.WriteLine($"Client — {c.SomeClientProperty}");
}
else if (person is Engineer e)
{
    Console.WriteLine($"Engineer — {e.SomeEngineerProperty}");
}

if (person is Client c)
{
    Console.WriteLine($"Client — {c.SomeClientProperty}");
}
else if (person is Engineer e)
{
    Console.WriteLine($"Engineer — {e.SomeEngineerProperty}");
}

the doctor monsterOP•2y ago

so if i got this right if variable person is of client type/ has client characteristics

Angius•2y ago

You can do property matching, yes

the doctor monsterOP•2y ago

what does the 'c' do after Client? is that just creating a new variable going forward?

Angius•2y ago

What I described is about the type

Person p1 = new Client();
Person p2 = new Engineer();

Person p1 = new Client();
Person p2 = new Engineer();

Yep, creates a new variable of the matched type

the doctor monsterOP•2y ago

great! will this thread stay open if I need to come back?

Angius•2y ago

It should, yea

the doctor monsterOP•2y ago

thanks so much by the way haven't even seen this in the textbook i got lmfao really appreciate it!

Angius•2y ago

Pattern matching is a fairly new feature

the doctor monsterOP•2y ago

ah I see thank god for libraries, this book is $70 and already old

Angius•2y ago

Yeah, books do go out of date fairly quickly We get a new version of .NET and C# every year, after all

the doctor monsterOP•2y ago

yeah the preface of this book literally says "there's a new version in 7 months" like why are you writin it then

Angius•2y ago

The features that are there stay the same, new ones are added on top. So you could think of that book as one that teaches a subset of C#

the doctor monsterOP•2y ago

that's a positive way of thinking

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Use Variable as Type